Medieval Theories of Future Contingents

The philosophical debate concerning the truth-value of singular
statements about future contingents derives from Chapter 9 of
Aristotle's treatise De interpretatione (Peri
hermeneias). In Chapters 7–8, Aristotle deals with
the contradictory pairs of assertoric statements which divide truth
and falsity so that one is true and the other is false. In Chapter 9
he raises the question of whether this holds for all assertoric
statements or whether there might be an exception with respect to
statements about singular future events or states of affairs which are
neither necessary nor impossible and hence may take place, or may not.
Aristotle's famous example is tomorrow's sea battle. Is the prediction
‘There will be a sea battle tomorrow’ necessarily true, if
it is true, and does its truth entail that the sea battle is
inevitable? After a discussion of deterministic arguments and the
absurdity of fatalism (18a34–19a22), Aristotle gives his
ambiguous reply in 19a23–39. Boethius's (c. 480–524) Latin
translation of De interpretatione had a long commentary
tradition through the Middle Ages, beginning from the twelfth
century. Boethius's own two commentaries were also very influential
and provided information about other ancient commentaries (Magee
2010). Chapter 9 was also dealt with in theological commentaries on
Peter Lombard's Sentences (I.38) and in separate treatises
(Isaac 1953, Lohr 1967–1974, Craig 1988, Marenbon 1993,
Braakhuis and Kneepkens 2003, Knuuttila 2010). Al-Farabi's
(c. 870–950) commentary on De interpretatione was influential
in medieval Arabic philosophy; Averroes (1126–1198) wrote
another Arabic commentary. (For future contingents in medieval Arabic
thought, see Marmura 1985, Adamson 2006.)

The debate about future contingents in modern philosophical logic
was revived by J. Łukasiewicz's works on three-valued logic
(1957, 1967). He thought that in order to avoid fatalistic
consequences, one should admit that the principle of bivalence (for any
proposition p, either p is true or p is
false) does not hold good for future contingent propositions. Arguing
that this was realized by Aristotle in Chapter 9 of De
interpretatione, Łukasiewicz attempted to formalize
Aristotle's position by introducing a third truth-value (neither
true nor false) for future contingent propositions and giving three-valued
truth-tables for truth-functional basic connectives. Many authors have
followed Łukasiewicz in taking Aristotle to restrict the principle
of bivalence, though they have not ascribed to him the details of
Łukasiewicz's system, which is problematic in many respects.
In arguing for the deterministic consequences of unrestricted
bivalence, Łukasiewicz himself assumed, and took Aristotle to
assume, that the truth of a proposition entails the necessity of its
truth. Logical determinism, therefore, is to be avoided by qualifying
the truth-values of future contingent propositions. The critics of this
view do not see any entailment relation between truth and necessity,
some of them maintaining that the illusion of logical determinism has
its roots in a tacit oscillation between a temporal and atemporal
predication of truth. The temporalized reading may be associated with
diachronic determination, certainty, necessity and other time-dependent
qualifications. Mixing these with non-deterministic atemporal
predications yields the wrong idea of fatalism (von Wright 1984,
52–67). It is also argued that even the temporalized predication of
truth carries no deterministic implications. (Sorabji 1980, 96–103;
Sorabji's example is that ‘even if it has already been true
that I am going to swim, I still retain the power to make it to have
been false’.)

The majority of Aristotelian scholars believe that the
confusing argument in De interpretatione 9 aims at avoiding
fatalism by restricting bivalence with respect to future contingent
predictions (Frede 1970, 1985, Sorabji 1980, Craig 1988, Weidemann
1994, Gaskin 1995). The second interpretation insists that
Aristotle's point is not to deny the truth of these statements,
but their being true in the same way as other statements are true. The
difference is that while the truth of other statements is necessary,
the truth of future contingent statements is not yet similarly
determined. This interpretation is associated with Aristotle's
remark that not everything which is actual and therefore necessary is
necessary without qualification (19a23). This is taken to mean that the
necessity of an event at a certain time does not imply that it was
inevitable. Aristotle speaks about singular future possibilities which
may be realized or remain unrealized and which may or may not cease to
be antecedent possibilities. (See De int. 19a13–17,
EN III.5, 1114a17–19, Met. VI.3.) In the same way
predictions may begin to be necessarily true or necessarily false. (For
various versions of this approach, see Anscombe 1956, Rescher 1963,
Hintikka 1973, Fine 1984, Judson 1988.)

The former interpretation, which restricts bivalence
with respect to future contingent statements, is called the
‘traditional’ or ‘standard’ interpretation. It is traditional because
some Stoics read Aristotle in this way, as Boethius reports in his
second commentary on Aristotle's De interpretatione:

Now some people – the Stoics among them – thought that
Aristotle says that future contingents are neither true nor false. For
they interpreted his saying that nothing [of that sort] is disposed
more to being than to not being as meaning that it makes no difference
whether they are thought false or true; for they considered them to be
neither true nor false [in Aristotle's view], but falsely.
(In Periherm. II, 208.1–4, trans. by N. Kretzmann)

On the basis of a note in Simplicius's commentary on
Aristotle's Categories (407.6–13), it is argued that
some Aristotelians also qualified the principle of bivalence. (For this
and other ancient deviations from the principle, see Sorabji 1980,
92–93.) On the other hand, future contingent propositions were regarded
as true or false in Stoic logic. The Stoics took the universally valid
principle of bivalence to imply the predetermination of all future
events. (See Cicero, De fato, 20–21; Bobzien 1998, 59–86.)

Boethius regarded the Stoic interpretation
of Aristotle's view as mistaken, his interpretation being based
on the terms ‘definitely’ true or false and
‘indefinitely’ true or false. These same terms were also used in Ammonius's
commentary (c. 435/445–517/526). Since this work was not known to
Boethius, both authors seem to have known some earlier Greek
discussions in which these qualifications were introduced.
(Ammonius's Greek commentary on De interpretatione 9 is
translated by D. Blank and Boethius's Latin commentaries by N.
Kretzmann in the same volume, with interpretative essays by R. Sorabji,
N. Kretzmann and M. Mignucci in 1998.) The contemporary reconstructions
of what Ammonius and Boethius meant can be divided into two groups.
According to one interpretation, Ammonius and Boethius ascribe to
Aristotle the view that the predictions of future contingent events and
their denials differ from other contradictory pairs, because truth and
falsity are not definitely distributed between them and the
propositions are consequently neither definitely true nor definitely
false. In answering the Stoic criticism, Boethius might have thought
that future contingent propositions have the disjunctive property of
being true-or-false, which would mean something other than simply
lacking a truth value. (For various interpretations of how Boethius
restricted bivalence, see Frede 1985, Craig 1988, Gaskin 1995,
Kretzmann 1998.) Another interpretation holds that future contingents
are not definitely true or false, because their truth-makers are not
yet determined, but are true or false in an indeterminate way. No
qualification of the principle of bivalence is involved. True
statements are either determinately true or simply (indeterminately)
true (Mignucci 1988, 1998; Seel 2000; Beets 2003 for Boethius's first
commentary). Ammonius and Boethius assumed that the definite truth of
predictions directly implies determinism. They also believed that
Aristotle denied the definite truth of predictions, but it is less
clear how they understood the indefinite truth of these (Sorabji
1998). In commenting on Aristotle's remark that 'what is necessarily is when it is (De interpretatione 19a23), Boethius explains that even though present things are temporally or conditionally necessary, they may be generically or antecedently contingent (In Periherm. I, 121.20–122.4; II, 241.7–243.28). He apparently thought that the truth of future contingent statements implies that things cannot be otherwise, for the assumed actuality of the truth-makers means that alternative prospectives are rendered temporally impossible.

In his longer commentary on De
interpretatione, Boethius says of God that ‘he knows future
events as happening contingently and not necessarily so that he does
not ignore the possibility that something else might take place’
(In Periherm. II, 226.9–12). Boethius also stresses that since
the truth of future contingents is not accessible to humans, the
predictions of the form ‘A sea battle will take place
tomorrow’ are false even when evaluated as past predictions of
what has taken place. What is false is the assertoric mode rather than
what is asserted (In Periherm. II, 211.26–213.18). In his
later treatise Consolatio philosophiae Boethius states that
‘I do not think that anybody would say that those things which
are happening now were not going to happen before they happened’
(V. 4.19) In this treatise, Boethius argues that God is atemporal and
has timeless knowledge of everything. God's timelessness involves
his having all time present to him simultaneously. God's
knowledge is not foreknowledge, since it is not temporally located, but
the predictions of future contingents are true or false from the point
of view of God's eternal knowledge of the things referred to
(V.6, 25–32; see also Augustine, City of God 11.21). It is
necessary that if God knows that p, then p. This ‘conditional
necessity’ does not imply the ‘simple necessity’ of p
(Consolatio philosophiae V, 6.27–30). Some medieval authors
read this distinction in Boethius and Augustine as a modal placement solution to the
problem of foreknowledge and free will (Matthews 2004). Thomas Aquinas, for example,
refers to Boethius's distinction using the terms necessitas
consequentiae and necessitas consequentis (Summa
contra gentiles I.67; De veritate I.23, ad 13).

In discussing statements such as ‘What is known by God
necessarily takes place’, Anselm of Canterbury (1033–1109)
distinguished between the antecedent and consequent necessity of things
which are known. The latter is the necessity of a thing's
actuality which is caused by the actuality of the thing itself. The
former is the necessity by which a thing exists because of an external
cause (Cur Deus homo 2.17, 125.6–126.2). Neither antecedent
knowledge nor antecedent truth has a compelling effect on things. In
explaining Mary's believing the truth of a prophetic statement
concerning the death of Christ, Anselm writes:

Therefore, since her faith was true faith it was necessary that
things would be as she believed. But if you are once again disturbed by
my saying “It was necessary…”, then remember that
the truth of the virgin's faith was not the cause of his dying
freely but that her faith was true faith because this was going to
happen. (Cur Deus homo 2.17, 124.27–125.3)

William of Champeaux (c. 1070–1122) dealt with an
argument against the compatibility between contingency and divine
omniscience which was discussed in Augustine's City of
God (V.9). In response to Cicero's De fato
and De divinatione, Augustine refuted the claim that the
possibility of events having happened otherwise implies the possibility
of error in God. William stated that the antecedent of the argument is
true but the consequent is false and therefore the consequence is not
valid (Lottin 1959, 195, Marenbon 1997, 226–227). Peter Abelard
(1079–1142/4) , in discussing the same example, applied the systematic
division between modal statements de sensu or in the compound
sense and modal statements de re or in the divided sense. (For
Abelard's modal terminology, see Super Perihermenias
3–47. Later authors used the expression de dicto instead of
de sensu.) Abelard's analysis of Cicero's argument
was often repeated in medieval theology, since it was put forward in
slightly modified form in Peter Lombard's Sententiae (c.
1157), which became the standard medieval introduction to theology.
Abelard states that when the proposition ‘A thing can be
otherwise than God knows it to be’ is read as a modal proposition de
sensu, the antecedent is false and the possibility of God's
error as a consequent would not follow even if the consequence were
valid. When the antecedent is read de re, it is true, but the
consequent is false, since if things were otherwise, then God would
possess different knowledge of them. This shows that the consequence is
not valid. Following Peter Abelard, Peter Lombard formulated the same
view in stating that ‘Things cannot be other than as God
foreknows them’ is true in the compound sense and false in the
divided sense. The truth of the compound sense saves God's
infallibility and the falsity of the divided sense expresses
God's freedom and the metaphysical contingency of the future (Peter Lombard,
Sententiae I.38.2; Peter Abelard, Logica
‘Ingredientibus’, 429.26–430.36; Dialectica,
217.27–219.24). It is assumed here that when a temporally definite statement is true, its denial may be possibly true.

Future contingent statements could be dealt with as
time-dependent future tense statement types with truth-values changing
in accordance with the time of assertion, as in Aristotle and
Hellenistic philosophy. (For the prevalence of temporally indefinite
sentences in ancient philosophy, see Hintikka 1973, Ch. 4; Bobzien
1998, 66–67, 100–101, 109–111.) In the theological context of
timeless divine omniscience, it was more natural to regard these
statements or their asserted content as atemporal. Abelard calls
statements propositions (propositio) and what is asserted by a
statement its dictum. He considered that a statement is
true or false when its dictum is true or false. In
dealing with prophesy, Abelard suggested that the dictum about a
singular event is first expressed by a future tense proposition and then
by present and past tense propositions. (For the nature of the
dictum, contrasted with the ‘facts’ and
‘propositions’ of twentieth-century philosophical jargon,
see Marenbon 1997, 202–209). The view of the atemporal propositional
content was developed further by twelfth-century authors who were later
called nominales. One of the theses of this group was
‘What is once true is always true.’ (See Iwakuma and
Ebbesen 1992, 196, 199–201, 205, 206 for the relevant texts. For the
history of the principle, see also Marenbon 1992, 58–61 and Ebbesen
1992, 73–74.) This thesis was often employed in
the discussions of the question of how the beliefs of Abraham and
others who lived before the coming of Christ and believed various
things about him were the same as the beliefs of those who live after
His coming. The reason for asking this was that the previous beliefs
were formulated in future tense statements and the latter in present or
past tense statements. According to the nominales, one could
deal with these problems by regarding as basic a temporally definite
propositional content the meaning of which is expressed by various
tensed expressions depending on when they are uttered. While tensed
statements about temporally definite singular events have a changing
truth-value, the corresponding non-tensed dicta are
unchangingly true or false (Nuchelmans 1973, 177–189; for some later examples, see also Nuchelmans 1980, Lewis 1995 and Goris 2001). Peter
of Poitiers (c. 1130–1205), one of the authors taking this approach, argued that while the singular statements about contingent things are immutably true or false because of God's eternal choice, their unchanging truth-value could be otherwise. God does not know contingent things through tensed statements, since their
truth-value is changeable. If God's knowledge is described by using tensed statements, analogously to the articles of faith before and after the coming of Christ, one should read them so that they signify the same (Peter of Poitiers, Sententiae I.7, 133–143; I.12.199–223;
I.14.328–253). This became a well-known position, since it was also employed in Peter Lombard's Sententiae (I.39.1; I.41.3.)

The theological formulations by Peter Abelard, Peter
Lombard and Peter of Poitiers discussed above exemplify twelfth-century
deviations from the Aristotelian thesis ‘What is necessarily is
when it is.’ This was traditionally understood as implying the
principle of the necessity of the present, which was not questioned in
ancient modal theories (Knuuttila 1993, Ch. 1). Since God's
knowledge about contingent things was regarded as unchangeable, the
contingency of this knowledge also implied the denial of the
Aristotelian equation of immutability with necessity, a denial regarded
as an explicit doctrine of the nominales (Ebbesen and Iwakuma
1992, 194). The new modal paradigm, which is more or less consciously
applied in these discussions of God's will, power, and knowledge,
could be characterized as the model of simultaneous alternatives. There
are three main examples of it in early medieval philosophy.

Abelard assumes that at a given instant of time, what
is actual is necessary in the sense that it can no longer be avoided,
but he argues that unrealized alternatives are possible at the same
time in the sense that they could have happened at that time. Some of
the alternatives of a singular being are real counterfactual
alternatives. These are unrealizable because of some previous change in
the conditions of the subject, and some are merely imaginable
alternatives, such as Socrates's being a bishop, which never had
a real basis in things. While often employing traditional ideas about
necessity and possibility, Abelard also developed ideas pertaining to
simultaneous alternatives. (See Martin 2003; Knuuttila 2008, 537–538).

Gilbert of Poitiers (1085/90–1154) stressed the idea
that natural regularities which are called natural necessities are not
absolute, since they are chosen by God and can be overridden by divine
power. This had become a widespread theological view in Gilbert's
time. Gilbert explained it in the light of the Augustinian view of
God's acting by divine will, which chooses between alternative
providential plans, and divine omnipotence as an executive power. There
is an interesting formulation of Plato's ‘Platonitas’
in Gilbert. This is said to include all of what Plato was, is and will
be as well as what he could be but never is. Even though Gilbert does
not explain why there is a modal element in the individual concept, it
was probably needed in order to speak about Plato in alternative
possible histories or, as in Abelard, about Socrates as a bishop.
Gilbert seems to have been the first to formulate an individual concept
in this way (Marenbon 2007, 158–159).

A third context of the systematic interest in simultaneous
alternatives was the new twelfth-century theory that declarative
singular statements or their contents should be primarily treated as
temporally definite and as having an unchanging truth-value. All
propositional contents pertaining to contingent things have a
truth-value on the basis of God's eternal choice. These
truth-values would be otherwise if the providential design of the
world were different in relevant respects. Robert Grosseteste
(1168/75–1253) taught that the opposites of actualized contingent
things are no longer realizable possibilities, though they are
possible alternatives in the sense that they could have been included
in God's eternal providential choice. Actual history is an
explication of one of the divine alternatives with respect to which
things are primarily called necessary, possible or
impossible. Necessities and possibilities at this basic level are
called modalities ‘from eternity and without
beginning’. Mathematical truths exemplify these
‘simple’ necessities. In addition there are necessities
and impossibilities which have a beginning and which are eternal
contingencies in the sense that they depend on God's free choice
(De libero arbitrio 168.26–170.33; 178.28–29). The contingency
of the divine acts of knowledge and will is based on an atemporal
causal priority between the powers of knowledge and the will and their
acts (178.24–26). Grosseteste's views are compared with those of Duns Scotus in Lewis (1996).

This was the innovative early medieval theory for
dealing with future contingent statements as
omnitemporally true or omnitemporally false or,
if these were tensed, as antecedently true or antecedently false
. The truth-values of statements about continget things, though temporally
immutable from the beginning of the world and also immutably known by
God, were metaphysically contingent. The consequence from knowledge or
truth to necessity, whether causal or semantic, was denied.
Metaphysical contingency was taken to depend on God's eternal and
free choice, which involved the acts of the created will being free. Anselm
formulated this traditional view, following Augustine, as follows:
‘It is both necessary that God foreknows what will come to be and
that God foreknows that something will freely come to be’ (De
concordia praescientiae et praedestinationis et gratiae Dei cum libero
arbitrio, 1.1; cf. Augustine, On Free Choice of the Will,
3.3.8). Anselm argued that that predictions are true or false and their
truth as correspondence can be understood as the correspondence to what
will happen, although what will contingently happen is not known to
human beings without supernatural help. This was the standard view of
the possibility of prophesy. (See the above quotation from
Anselm's Cur Deus homo; Peter Abelard, Logica
‘Ingredientibus’, 426–429; Anonymous, Summa Duacensis,
129–30.)

Early medieval authors were well acquainted with the
conception of God's eternal and timeless knowledge in Augustine
and Boethius. This aspect of the question of the divine knowledge and
future contingents became a central issue in Thomas Aquinas's theory of God's
knowledge. According to Aquinas, God is the timeless and eternal ground
of temporal beings which are timelessly present to God's eternal
vision. God does not know temporal things merely as existing in his
cognition, but grasps all combinations of things in particular times by
one eternal vision. These are timelessly present to God, who has
immediate knowledge of them and their relative temporal order, though
none of them is past or future with respect to His cognition
(Sent. I.38.1.4–5, Summa contra gentiles I.66,
Summa theologiae I.14.9, 14). Things seen as actual are
necessary by supposition (i. e., with respect to God's knowledge
and providential plan), but many of them are contingent with respect to
their proximate causes (Sent. I.38.1.5, Summa contra
gentiles I.67, Summa theologiae I, 14.13, De
veritate 2.12). The ultimate source of the actuality of the
created order is the divine will (In Periherm. I.14, 197). The
whole of world history is known by God's eternal and immutable
vision, which includes the knowledge of things which are future
contingents in the temporal order. This indirectly makes future contingent
propositions true or false – otherwise there could not be true
prophetic predictions (Summa theologiae II-2, 171.6). Aquinas assumes, like Boethius, that the truth of future contingent propositions as such would make everything necessary (In Periherm. I.13, 173). For
various interpretations of Aquinas's view, see Wippel 1985, Craig
1988, 99–126, Goris 1996, Marenbon 2005.

Medieval critics found the idea of the non-temporal
presence of each instant of time to God's eternal vision
problematic. (See John Duns Scotus, Lectura I.39.1–5, 23, 27,
85, 87, and further references in Hoenen 1993, 169–70.) It is also asked how Aquinas's view of God's essential simplicity and immutability is compatible with the view that God's eternal choice could be otherwise and the voluntary
acts of created beings could be other than what is known by God. (See
Stump 2003, 100–127.)

Mignucci's account of how Ammonius and Boethius understood the
distinction between definite and indefinite truth is roughly speaking
the same as the explanation of these terms in Peter Abelard's
interpretation of De interpretatione 9. Abelard believed that
Aristotle assumed that future contingent statements are true or false,
though not determinately true or false before the actuality of the
things to which they refer (Dialectica 213.17–20). Abelard uses the notions of ‘determinate/indeterminate’ itstead of the Boethian ‘definite/indefinite’, as most medieval authors did. He retained the principle of bivalence for
all assertoric statements, but rejected the universal application of
the stronger principle that every assertoric statement is determinately
true or determinately false. According to Abelard, the notions of
‘determinate’ or ‘indeterminate’ apply primarily to
the truth-makers of assertions and secondarily to assertions
themselves:

But as the obtaining of future contingent states of affairs is indeterminate, similarly the propositions which enunciate these are said to be indeterminately true or false, for those which are true are indeterminately true and those which are false are indeterminately false, in acccordance with the indeterminate obtaining of what is predicted. Dialectica 211.30–32)

Abelard was particularly interested in the question of
whether the present truth of statements about future contingent events
are themselves determinate; i. e., whether ‘The sentence
‘Socrates will eat tomorrow’ is true’, if true, is
determinately true. Denying this, he restricted the principle that all
past and present true propositions are determinately true. Abelard also
distinguished between determinateness and certainty. Future contingent
propositions may be certain if they are revealed by angels, for
example, but they are not knowable of themselves and not determinately
true. (See Logica ‘Ingredientibus’ 420.12–422.40; Dialectica 211.32–212.23; Lewis 1987.)

The ‘traditional’ interpretation is put forward in an anonymous twelfth-century commentary on De interpretatione, edited by M. Dal Pra, which is often probably mistakenly attributed to Abelard. Applying Boethius's distinction between definitely and indefinitely true statements, the author argues that future contingent statements are merely disjunctively true or false (tantum sub disjunctione); 100.13–19; 112.8–113.3). They are true-or-false.

While Abelard thought that the universal validity of the principle
of bivalence was an Aristotelian view, thirteenth-century commentators
argued for the traditional interpretation. Albert the Great and Thomas
Aquinas took Aristotle to be arguing in De interpretatione 9
that if every contradictory pair divides truth and falsity in a
determinate way and the members are consequently determinately true or
false, all things must determinately be or not be. He then refutes the
consequent by referring to various contingent things. It follows that
the antecedent cannot be true and future contingent propositions are
not determinately true or determinately false. They are true-or-false
under disjunction (Albert the Great, Liber Perihermeneias,
I.5.4–6, 418–422; Thomas Aquinas, In Aristotelis Peri
hermeneias expositio, I.13, 170–172; I.15, 202–203).
The same interpretation of Aristotle is found in Arabic commentators
Abū Nasr al-Fārābī and
Averroes. (See Al-Farabi'sCommentary and Short Treatise
on Aristotle's De interpretatione, trans. F. Zimmermann, lxviii,
75–76, 78–79, 91–92, 244–245, and
Averroes's Middle Commentary on Aristotle's De
interpretatione, 82va.) Al-Fārābī's own view was that
future contingents are either true or false (94–96; Marmura
1985, Adamson 2006). Among Latin authors the traditional
interpretation of Aristotle's view was put forward by many later
commentators, such as John Duns Scotus, Quaestiones in libros
Perihermenias Aristotelis, I.7–8 (179–181); Walter
Burley, Commentarius in librum Perihermeneias Aristotelis,
92, 95–96; William Ockham, Expositio in Librum Perihermenias
Aristotelis I.6.15; Peter Auriol, Sent. I.38.3,
817–828; Gregory of Rimini,
Sent. I.38.1.1 (238–243); Peter of Ailly, Quaestiones
super Sent. I.11.1A). In his Supercommentary on
Averroes's Commentary on Aristotle's De
interpretatione, the Jewish philosopher Levi ben Gerson (Gersonides,
1288–1344) states that positing a truth value for future contingents
leads to absurdity (83r; Rudavsky 1985, 166). John Buridan read
Aristotle in the same way as Abelard. All assertoric statements are
true or false though those about future contingents are not
determinately true or false (Questiones longe super librum
Perihermeneias I.10). Since theologians usually thought that
divine omniscience and prophecy presupposed unrestricted bivalence, the discussion of future
contingents was divided into historical constructions of
Aristotle's view, mostly in accordance with the traditional interpretation, and the systematic discussions in theology which
usually followed the Abelardian lines. Later examples of the traditional interpretation of Aristotle's view include George of Brussels, Logica magistri Georgii inserto textu Bricoti, 51rv; Iodocus Trutfetter, Summulae totius logicae
II.1 (LL3v–4v); Veteris artis…Perihermeneiasque
expositio (g1r); see also Baudry (1950), 206. (For medieval interpretations, see Weidemann 1994; Gaskin 1995; Knuuttila 2010.)

The most influential late medieval approach to future contingents
was included in John Duns Scotus's theory of metaphysics as a
transcendental science in which the meaning of the univocal notion of
being (ens) was defined as ‘that to which to be is not
repugnant’. Beings in this metaphysical sense are actual things
as well as non-actual possible things, the imagined actuality of which
does not include contradiction. Scotus explains that this unusually
broad notion of being is justified because possible beings differ from
the absolute nothingness of impossible things, the concepts of which
are contradictory (Honnefelder 2005.)

In the Augustinian tradition metaphysical possibilities
were ultimately based on the divine essence and represented the ways in
which it could be imitated by created things. According to Scotus, when
God as an omniscient being knows all possibilities, he does not know
them by turning first to his essence. Possibilities can be known in
themselves; in fact, they would be what they are even if there were no
God. Scotus calls the propositional formulations of pure possibilities
logical possibilities (possibile logicum). These express
things and states of affairs to which it is not repugnant to be.
Possibilities as such have no kind of existence of their own, but are
real in the sense that they form the precondition for everything that
is or can be. (For Scotus's modal theory, see Vos et al. 1994, Knuuttila 1996,
Normore 2003, Honnefelder 2005.) A great deal of Scotus's
discussion of metaphysical themes concentrates on the modal explication
of being and the disjunctive transcendental notions of necessity and
contingency. Scotus takes it as an obvious fact that there are
contingent states of affairs which in his view could have not been at
that very moment of time at which they are (Ord. I.2.1.1–2,
86). This idea of simultaneous alternatives differed from the
traditional view of the necessity of the present and played and
important role in Scotus's proofs of the existence of a necessary
first being which acts as the free first cause of the contingent
world.

God's omniscience involves all possibilities and,
as objects of God's knowledge, they necessarily receive
intelligible or objective being. Some of these are included in
God's providential plan of creation and will receive actual
being. The description of a possible state of affairs at a certain moment consists
of compossible possibilities. Since finite beings are contingently
actual, alternative possibilities are possible with respect to the same
time, though they are not compossible with what is actual. According to
Scotus, impossibilities are incompossibilities between possible
ingredients, such as Socrates's sitting at a certain time and
Socrates's not sitting at that same time (Lect. I.39.1–5, 62–63; Ord. I.35, 32, 49–51;
Ord. I.36, 60–1; Ord. I.43, 5–7, 14).

Scotus's modal metaphysics incorporates many
ideas from the early medieval model which was developed by Abelard and
the nominales, such as the denial of the necessity of the
present, the distinction between immutability and necessity and the
universal validity of bivalence. Giving up the Boethian-Thomistic view of the atemporal
presence of the flux of time to God, Scotus explains God's knowledge of the truth-value of future contingent propositions as a knowledge of which of the possible scenarios is chosen to be actual (Lect. I.39.1–5, 44). The definite truth-values of the propositions about possible events do not make them necessary, many of these being acts of the will which as a free cause chooses between alternatives without being determined. (For some discussions of Scotus's view of the free acts of the will, see Dumont 2001; Normore 2003, 141–145; Langston 2010.)

William Ockham criticized Scotus's attempt to explain the contingency of God's choice
by distinguishing between the instants of nature in God which represent
conceptual succession without separation or interval, for example, the
instant of the will encountering opposite alternatives and the instant
of choosing one of these. (See Sent. I.38.1 (578, 581); Adams 1987, 1130–1136.) Ockham followed
Scotus in believing that God's choice could be other than it is.
He was dissatisfied with Scotus's explanation without having any
of his own. Ockham also criticized the view that God knows future free
acts through his own acts of the will as their ultimate cause, which
he, like many of his contemporaries and later commentators, treats as
Scotus's position (Sent. I.38.1 (582–583). In fact this was Henry of Ghent's view to which Scotus only half-heartedly subscribed, trying to find a formulation with less discursiveness in God. Apart from these subtilities, the main problem of Scotus's approach was considered to be how the idea of God's making propositions true is compatible with human free will. (See Hoenen 1993, 177–179; Söder 1999, 177–183; Schabel 2000, 43–46.)

Ockham believed, as Scotus did, that future contingent propositions
are true or false, that created wills are non-determined free causes
and that God knows contingent events without their being
simultaneously present to God. (For Ockham's view and the relevant
texts, see Adams and Kretzmann 1983.) While Scotus preferred to
distinguish God's eternal knowledge and choice from the temporal order
sharply (Lect. I.39.1–2, n. 28, 85; Ord. I.40,
n. 8), Ockham thought that they can be treated as temporally
past. This led him to ask how God's foreknowledge as something past
and hence seemingly necessary is compatible with the contingency of
the future things. Ockham's answer was that even though God's
foreknowledge is past, its content is future, and the past truth of
future contingent propositions does not fall under the necessity of
the past (Sent. I.38.1 (587), Tractatus de
praedestinatione 515–516). Many influential late thinkers
embraced this idea. (See Robert Holkot, Sent. II.2
in Seeing the Future Clearly, 127, 145–146; Gregory of
Rimini, Sent. I.38.2.3 (302–303); Pierre
d'Ailly,Quaestiones super Sent. I.11.3S.) This is also the
hallmark of what is called the Ockhamist view of divine foreknowledge
in contemporary philosophical theology (Zagzebski 1991,
66–97). For texts and studies on late medieval
controversies related to foreknowledge and freedom, see Schabel 2000,
2003, 2004, 2007; Schabel, Friedman and Balcoyiannopoulou 2001;
Rossini and Schabel 2005; Martin 2004.

Many early fourteenth-century authors were interested
in the distinctions between determinate and indeterminate truth and
falsity. Ockham characterized all prospective truths, whether necessary
or contingent, as immutable and therefore determinate, but there were
other suggestions as well (Normore 1982, 1993, Genest 1992, Gelber
2004, 224–250). It was increasingly believed that in Aristotle future contingent statements were neither true nor false, and some authors
associated the notions of indeterminate truth and falsity with the
denial of bivalence for future contingent statements. One of these was
Peter Auriol, who argued that since these lack a truth value, even God
is aware of the future in a way which does not imply that future
contingent statements are true or false (Schabel 2000, 67–123). Auriol's position inspired much discussion until early sixteenth century. It came to be regarded as heretical when a
Papal commission made a decision about the theses of Peter de Rivo, who
defended a view similar to that of Auriol. Some of de Rivo's
statements were officially damned in 1474 by Pope Sixtus IV (Baudry
1950, Schabel 1995; 1996; 2000, 315–336; 2004).

A central question for those who gave up the Thomist simultaneity view was how God can eternally know the acts of the will which is a free cause? An influential answer was offerred in the theory of middle knowledge by Luis de Molina
(1535–1600). In addition to the knowledge of all possibilities and the
possibilities which will be actualized in the providentially chosen
history, God has a third kind of knowledge (scientia media),
which comprises the hypothetical truths about possible beings. In
creating the world, God knows what possible creatures would do in any
possible situation (Freddoso 1988). Molina's ‘middle
knowledge’ theory about counterfactuals of freedom was actively
debated in the sixteenth and seventeenth century and has remained a
living issue in the philosophy of religion (Dekker 2000).

Abū Nasr al-Fārābī, Al-Farabi's
Commentary and Short Treatise on Aristotle's De
interpretatione, trans. with introduction and notes by
F.W. Zimmermann, The British Academy Classical and Medieval Logic
Texts 3 (Oxford: Oxford University Press, 1981).

–––, (2004), ‘John Mair on Future
Contingency’, in R. Friedman and S. Ebbesen (eds.), John
Buridan and Beyond: Topics in the Language Sciences,
1300–1700 (Copenhagen: The Royal Danish Academy of Sciences
and Letters), 183–201.